| Abstract: | Four unarmored heterotrophic dinoflagellates were isolated from the coastal waters of southern Korea. The rDNA sequences of four clonal cultures were determined, and the morphology of one of the four strains was examined using light and scanning and transmission electron microscopy. The large subunit (LSU) and small subunit (SSU) rDNA sequences of each of the strains differed by 0–0.9% from those of the other strains, and the SSU rDNA sequence of the strain differed by 1.8–4.4% from those of other Gyrodinium species, whereas the LSU (D1–D2) rDNA sequence differed by 12.4–22.2%. Furthermore, phylogenetic trees showed that Gyrodinium jinhaense n. sp. formed a distinctive clade among the other Gyrodinium species. Meanwhile, microscopy revealed an elliptical bisected apical structure complex and a cingulum that was displaced by approximately one‐quarter of the cell length, which confirmed that the dinoflagellate belonged to the genus Gyrodinium. However, the cell surface was ornamented with 16 longitudinal striations, both on the episome and hyposome, unlike other Gyrodinium species. Furthermore, the cells were observed to have pusule systems and trichocysts but lacked mucocysts. Based on morphology and molecular data, we consider this strain to be a new species in the genus Gyrodinium and thus, propose that it be assigned to the name G. jinhaense n. sp. |
